2) Whisk together the applesauce, buttermilk, treacle, and sugar in a medium bowl. Add the eggs and whisk until smooth.
3) Sift the flour, bicarbonate of soda, baking powder, ginger, cinnamon, salt, cloves, and allspice together in a large bowl.
4) Add the treacle mixture into the flour mixture and whisk until combined to form a smooth batter.
5)Bring the water and butter to the boil in a small saucepan. Add the hot liquid to the batter, and whisk until just combined. Pour the batter into the prepared tin.
6) Bake the cake in the center of the oven for about 40 minutes, until a toothpick inserted into the center comes out clean. Cool the cake in the tin on a rack. Cut into 12 squares and serve with the yoghurt sauce.
7) To make Yoghurt Sauce: Line a strainer with cheesecloth or a coffee filter and set over a small bowl. Stir the yoghurt, and put it in the strainer. Set aside at room temperature to drain and thicken, for about 30 minutes. Discard the excess liquid. In a small bowl, combine the thickened yoghurt with the sugar. Serve.